Method of making a nipple-electrode joint

ABSTRACT

The invention relates to nipple-electrode assemblies and joints, such as those used in electric arc furnaces, and to a means of distributing thread clearance throughout the assembly and/or joint. These means include the pre-positioning of the nipple in the socket of the electrode section into which the nipple is threaded so as to provide a clearance between the non-load bearing flanks of the threads of said threaded nipple and said threaded electrode socket and the placing within the space between the base of the nipple and the bottom of the socket of the electrode section a hot, non-gaseous fluid, carbonizable material which solidifies upon cooling, thereby preparing a preassembly wherein the nipple is fixed in the electrode section, thereby maintaining the aforedescribed pre-positioning and thread clearance and thereby also providing room for thermal expansion of the threads of the connection. The hot, carbonizable material is introduced into the space between the base of the nipple and the bottom of the socket, while in a hot, fluid condition, through a hole in the nipple after the nipple has been threaded into the electrode socket, after which the carbonizable material solidifies. Upon connection of the projecting end of the nipple into a socket of an electrode section and use in a column of electrodes in an electric arc furnace, the solidified carbonizable material again becomes heated, melts and some of it flows downwardly through the hole into the corresponding space in the socket of the electrode section of the column and then becomes solid and carbonizes due to the heat encountered, thereby locking the nipple in the sockets of both electrode sections joined.

United States Patent 1 Gazda 1 Feb. 27, 1973 METHOD OF MAKING A NIPPLE-ELECTRODE JOINT [7 5,] Inventor: Irvin William Gazda,.lohnson City,

Tenn.

[73] Assignee: Great Lakes Carbon Corporation,

' New York, NY.

[22] Filed: Feb. 9, 1971 2'11 Appl. No.: 113,995

[52] U.S. Cl. ..29/25.14, 13/18, 287/127 E [51] Int. Cl ..H01j 9/00 [58]Field of Search....29/25.l4, 25.13, 25.11, 470.5;

[56] References Cited UNITED STATES PATENTS 3,517,954 6/1970 Snyder eta1 ..287/127 2,510,230 6/1950 Johnson et al ..1 3/18 3,140,967 7/1964Kaufmann et al. ..l56/91 Primary Examiner-J. Spencer OverholserAssistant ExaminerRichard B. Lazarus Attorney-Wallace F. Neyerlin [57]ABSTRACT The invention relates to nipple-electrode assemblies andjoints, such as those used in electric arc furnaces, and to a means ofdistributing thread clearance throughout the assembly and/or joint.These means include the pre-positioning of the nipple in the socket ofthe electrode section into which the nipple is threaded so as to providea clearance between the non-load bearing flanks of the threads of saidthreaded nipple and said threaded electrode socket and the placingwithin the space between the base of the nipple and the bottom of thesocket of the electrode section a hot, non-gaseous fluid, carbonizablematerial which solidifies upon cooling, thereby preparing a preassemblywherein the nipple is fixed in the electrode section, therebymaintaining the aforedescribed prepositioning and thread clearance andthereby also providing room for thermal expansion of the threads of theconnection. The hot, carbonizable material is introduced into the spacebetween the base of the nipple and the bottom of the socket, while in ahot, fluid condition, through a hole in the nipple after the nipple hasbeen threaded into the electrode socket, after which the carbonizablematerial solidifies. Upon connection of the projecting end of the nippleinto a socket of an electrode section and use in a column of electrodesin an electric arc furnace, the solidified carbonizable material againbecomes heated, melts and some of it flows downwardly through the holeinto the corresponding space in the socket of the electrode section ofthe column and then becomes solid and carbonizes due to the heatencountered, thereby locking the nipple in the sockets of both electrodesections joined.

8 Claims, 8 Drawing Figures PATENTEDFEBZYIQB I sumsnm' FIG. 3a

FIG. 3b

PATENIEUFEBZ? i973 SHEET 0F 4 FIGS METHOD OF MAKING A NIPPLE-ELECTRODEJOINT BACKGROUND OF THE INVENTION 1 Field of the Invention Thisinvention relates to the field of graphite electrodes such as those usedin electric arc furnaces and like equipment, wherein the electrodes areconsumed in use and wherein the electrodes must be continually fed intothe furnace or other equipment where they are used.

In ,order to facilitate this continual feed, the electrode sections aresuitably bored and threaded at each 8 end to provide juncture meansthrough a correspondingly shaped and threaded nipple. In this manner, anew electrodeis joined to the one being consumed by inserting a nippleinto the bore of either the new or partially consumed electrode sectionand joining the composite electrode section-nipple assembly to the otherelectrode section. Such nipples and their corresponding bore holes inthe electrode sections may have threaded sides which are parallel to thenipple axis. It is generally more customary and advantageous, however,to taper the nipple so that its largest diameter is at its middle and isalso at the plane of contact between the electrode sections. Such atapered nipple is screwed into place in a correspondingly taperedthreaded bore or socket of the electrode section with the small diameterend or nipple base going furthest into the electrodebody'. ln threadingthe tapered nipples for use in joining electrode sections, the threaddepth is generally the same whether measured at the small diameter endsor bases or at the large diameter center. lt is also usual that in theassembled joint each thread will possess a loaded flank, which is nearerthe geometric center of the nipple, and a non-load bearing or idle flankwhich is opposite to the loaded flank.

:(That .is, the idle flank is the flank nearer the ends of electrodesections to loosen and to become unwound from around the connectingnipples thereby frequently causing high power and/or graphite materiallosses due to increased electrical resistances at the joints and/or anelectrode section becoming completely unthreaded and falling into themetal bath at'the bottom of the furnace.

2. Description of the Prior Art There has been a well recognized need tomore evenly distribute the aforedescribed clearance differences in orderto reduce or counteract thermal stresses which build up due to lack ofexpansion room and result in cracking the joint, and various methodshave been proposed by those skilled in the art to 'accomplishsubstantially even distribution of thread clearance. For example, thisproblem and several Nos. 2,970,854; 2,957,716; 3,088,762; 3,134,616;3,140,967; 3,517,954; and 3,517,957; and also in German Pat. No.1,091,253.

The difliculties involved with electrode sections becoming loose and/orunwound from the nipple have also been well recognized and US. Pat. Nos.2,510,230; 2,735,705; 2,828,162; 2,862,748;- and 3,048,433 offerteachings of typical ways which have been suggested for overcoming thisproblem.

The present invention also relates to and is concerned with a more evendistribution of clearance between the threads of the nipple and theelectrode sockets and consequent reduction in thermal stresses between anipple andthe electrode sections into which it is threaded, and alsorelates to making the connections between the electrode sections andconnecting nipples tighter and less able to become unwound, and

offers a novel and advantageous approach for simultaneouslyaccomplishing each of these conditions or objectives.

SUMMARY OF THE INVENTION It is an object of the present invention toprovide a nipple-electrode section assembly or pre-assembly in whichthere is a more evenly distributed clearance (as compared toconventional commercial practices) between the idle or non-load bearingflanks of the threads of the nipple and the threads of the electrodesection socket, so as to provide room for thermal expansion of saidthreads.

It is another object of this invention to substantially evenlydistribute thread'clearance throughout a nippleelectrode sectionpre-assembly, and also throughout an entire electrode joint assemblycomprising two electrode sections having threaded sockets in the endsthereof and a nipple threaded into said sockets, joining the electrodesections together. It is another object of this invention to accomplishthe-aforesaid more even distribution of thread clearance in anadvantageous and practical manner while simultaneously makingthe'connections between the electrode sections and connecting nippletighter and less able-to become unwound and proposed solutions for sameare discussed in US. Pat.

in a manner which is also novel as compared to techniques which havebeen suggested or taught by the prior art for solving these problems. I

The invention, in a preferred embodiment, comprises the makingof animproved nipple-electrode section pre-assembly, such as described, by:

a. Providing a hole starting at a point in an end face of one-half ofthe nipple and terminating at a point in the surface of the other halfof the nipple;

b. pre-positioning the nipple nipple and the in of the electrode sectionby threading an end thereof possessing a hole in its end face into theinternally threaded socket so as to provide s space between the base ofthe nipple and the bottom of the electrode section socket and aclearance between the non-load bearing flanks of the threads of saidthreaded nipple and the opposing faces of the threads of the electrodesocket, said non-load bearing flanks of the threads being those nearerto the ends than to the'geornetric center of the nipple; I

c..introducing a hot, non-gaseous fluid, carbonizable material throughthe exposed end of the hole of the nipple in sufficient quantity so thatimmediately upon in- -between the base of the nipple and the bottom ofthe socket of the electrode section without undergoing anysubsequentexpansion; and

d. permitting said hot fluid material to become substantially solid bycooling it to ambient temperature, thereby fixing the nipple in theelectrode section and thereby also maintaining the thermal expansion ofthe threads of the connection.

Preferably the pre-positioning of the nipple in step b is effected byutilizing a temporary positioning means, such as is describedhereinafter, which temporarypositioning means is removed after the hotfluid material has been cooled and become substantially solid, as instep d.

The invention embraces not only the process of making the connection orpre-assembly but also the nippleelectrode-section pre-assembly itself,and the electrode joint assembly made by coupling a secondelectrodesection to the improved nipple-electrode section preassembly,and also the process of making said joint as-' sembly.

Other objects, and coincident advantages, and a complete understandingof the invention will be apparent to those skilled in the art after astudy of the drawings, and a reading of the specification and claims.

BRIEF DESCRIPTION OF THE DRAWINGS It has been found that the foregoingobjects are achievable by making a nipple-electrode section preassemblysuch as illustrated in vertical cross-section in FIG. 1 and by usingsuch a pre-assembly as a part of each joint assembly used in theelectrode column.

FIG. 2 illustrates auxiliary equipment,viz. a centering jig, which maybe used as a temporary positioning means in carrying out the processesof or in making the pre-assemblies of the present invention.

FIG. 3 illustrates in FIGS. 3a, 3b, 3c and 3d embodiments of fouralternate hole orientations or arrangements in the nipple that may beemployed in the present invention besides the use simply of a centralhole as illustrated in FIGS. 1 and 2. The nipple must always possess atleast one hole extending in an axial or generally lengthwise direction(c.f. FlGll), but, as is apparent from FIG. 3d, one or more additionalholes may also sometimes be employed in conjunction therewith. (This isdiscussed in more detail hereinafter). The axial or generally lengthwisehole must always start at a point in an end face of one-half of thenipple and terminate at a point in the surface at the other half of thenipple. Preferably the lengthwise hole will extend from one end face ofthe nipple to the other end face, as illustrated in FIGS. 1, 3a, 3b and3d. Less preferably it may also terminate at a point in the surface ofthe other half of the nipple which is not in the opposite end face ofthe nipple.

FIG. 30 illustratesv this possible embodiment of the invention.

FIGS. 4 and 5 illustrate the final assembled joints described in thepresent invention, (employing the preassembly illustrated in FIGS. 1 and2), FIG. 4 illustrating the condition of the joint when first assembledand FIG. 5 illustrating the condition of the joint thereafter afterthere has been melting and downward flowing of some of the carbonizablematerial from the space between the base of the nipple and the bottom ofthe socket of the electrode section of the pre-assembly.

DETAILED DESCRIPTION OF THE DRAWINGS AND OF THE PREFERRED EMBODIMENTS Asillustrated in FIG. 1, the nipple l, which as previously stated ispreferably tapered, was threaded into a correspondingly tapered andthreaded socket of electrode section 2. The nipple was provided with acentral, axial or longitudinal hole 8 which extended lengthwise from oneend face 6 of the nipple to the other end face 9. The nipple had a majordiameter of 10 74 inches, the diameter of the longitudinal hole was 1 isinch and the diameter of the electrode section 2 was 20 inches. Thenipple also had a one-third pitch, i.e. three threads per inch, and ataper of l to 6, i.e. its radius decreased by 1 inch for every 6 inchesof length of the nipple away from the maximum diameter. The nipple wasthreaded into the socket until its major diameter, indicated generallyat 3, coincided approximately with the plane of the face 4 of theelectrode section and until it was hand-tight", i.e. until the threadsof both the nipple and electrode socket section were completely engaged.The nipple was then pre-positioned in the electrode section socket bybeing backed-off a slight amount such as an eighth tum (i.e. 45) so asto provide a clearance between the idle flanks of the threads of saidthreaded nipple and said threaded electrode socket. A centering jigtemporary positioning means was employed during the pre-positioning ofthe nipple. (More is stated resuch fluid, carbonizable materials andtheir nature or composition hereinafter). An excess of the hot, fluid,carbonizable material was employed (and this is typical) and thisextended partially up the lengthwise or longitudinal hole such as tolevel 10, which is typically at least midway up the hole 8 and morepreferably to a level such as will substantially fill the hole 8 as wellas the space 5. As the material cooled to ambient temperature itsolidified and substantially or completely filled any void area in thespace 5 and also served to fix the nipple in the desired position in theelectrode socket. The solidification of the material also maintained theaforediscussed pre-positioning and thread clearance of the nipple,thereby also providing room for thermal expansion of the threads of theconnection. The pre-positioning of the nipple also caused the upperfaces or load-bearing flanks l1 (viz. the flanks nearer the geometriccenter of the nipple) to contact the mating faces of the threads of thesocket and also caused or created a slight gap or clearance 12 at theidle or nonload bearing flanks or sides 13 of the thread, viz. the

flanks nearer the end 6 of the nipple. (It is clear from, the foregoingdiscussion, of course, that the pre-as- Drilling the hole 8 off-centermay also be resorted to and typical ways that this might be done areillustrate in FIG. 3, embodiments 3a, 3b and 3c. In FIG. 3a the axis ofthe hole is parallel with the axis of the nipple. In FIG. 3b the holeextends lengthwise from one end face of the nipple to the other end facebut the hole is at an angle 7 to the nipple axis. In FIG. 3c the holestarts at a point in an end face of one-half of the nipple andterminates at a point in the surface of the other half of the nipple (asdo also the holes of FIGS. 1, 3a and 3b) but does not fully extend tothe other end face of the nipple. In other words it exits on thethreaded lateral surface of the nipple. This is not as desirable asexiting from a position on r the end face of the nipple but it doesdefine an operable position for introducing the hot fluid material intothe 'hole and is within the scope of the present invention.

Also, in this embodiment, the point of exit of the hole on the threadedlateral surface is preferably nearer the end than the center of thenipple but is also typically a distance of at least about one-sixth thelength of the nipple from the end.

FIG. 3d illustrates the use of two lateral or generally transverse holes8a and 8b which intersect or connect at an angle with the lengthwisehole 8. These holes are typically of smaller diameter than thelengthwise hole 8. FIGS. 3a, 3b, 3c and 3d also show the typicalposition of the carbonizable material within the clearance space 5 andthe holes 8 (and 8a and 8b) of the pre-assembly before the exposednipple end of the pre-assembly is connected to another electrodesection.

, The invention is intended'to cover pre-positioning of the nipple so asto cause a clearance between the idle flanks of the nipple and thethreads of the socket of the electrode section no matter how thepre-positioning of the nipple is effected so long as the other steps ofthe invention are practiced. However, it is preferred that an auxiliarydevice or temporary positioning means such as a centering jig" be usedin order to provide optimum pre-positioning of the nipple.

(The backing-off of 45 of the nipple in the embodiment just described insatisfactory for a nipple having a pitch and taper as set forth. In amore general sense, the number of degrees"backed-ofi'" will depend onthe pitch and taper of the nipple because the clearance between thethreads is a function of these two variables. For standard nippleshaving a one-third pitch and a taper of l to 6, the number of degreesbacked off will typically be a value from about 45 to about 90; forstandard nipples having a one-fourth pitch (four threads per inch and ataper of 1 to 6, the number of degrees backed off will typically be avalue from about 60 to about 135).

In the embodiment'of FIG. 2, such a centering jig is illustrated, and isemployed in order to pre-position the nipple in the electrode socket andin order to provide a clearance at the idle flank .of the threads of thenipple and the internal threads of the electrode section into which thenipple is threaded.

The centering jig consists of an internally threaded plate 18 which isthreaded onto one end of the nipple 1. Casters .19 are coupled throughholes in the centering plate to la inch diameter bore air cylinders 17.Three casters and three .air cylinders are typically used, the castersbeing so spaced as to form an equilateral triangle against the face 4 ofthe electrode section 2. A

source of air (not shown) provides air under pressure to air cylinders17. The arrangement is such that the casters 19 push in one directionagainst the face of the electrode section while the threaded plate 18pulls the nipple 1 in the opposite direction, thus applying an axialpressure or force upon the nipple and pre-positioning the nipple in thesocket of the electrode section, and thus providing a. clearance betweenthe non-load bearing or idle flanks 13 of the threads of the nipple andthe threads of the electrode section. (Axial or lengthwise andtransverse or clockwise directions are shown in FIG. 1).

.free end of the nipple. The centering jig device was then tumed on" bypressurizing the air cylinders 17 to 200 psi each. (Casters 19 were incontact with the face 4 of the electrode section 2). By doing this anaxial force was exerted upon the nipple in a direction away from theelectrode section. While this axial force was still being applied, thenipple was backed off 45 thus providing a clearance between the idleflanks 13 of the threads of the nipple and the opposing flanks of thethreads of the socket of the electrode section 2 and thuspre-positioning the nipple in the socket of the electrode section. Thisaxial pressure also caused the loadbearing flanks ll. of ,thethreads ofthe nipple (viz. the flanks nearerthe geometric center of the nipple) toremain in direct and close contact with the mating threads of theelectrode socket. Coal tar pitch, having a melting point of C, washeated to 200C and a measured amount of this hot molten fluid wasinjected through the longitudinal hole 8 and into the cavity or space 5between the base 6 of the nipple and the base or bottom 7 of theelectrode section socket. A sufficient amount of the pitch was employedso as to, immediately upon introduction without undergoing anysubsequent expansion, substantially fill the space 5 and extend well upinto the longitudinal bore 8, such as to a height as illustrated inFIG. 1. The nipple-electrode section pre-assembly was maintained in afixed position until the molten pitch material had cooled tosubstantially ambient temperature, thereby causing the pitch to becomesubstantially solid, after which the pressure was released and the jigremoved. (A typical cooling time is from 5 to 10 minutes). The pitchsolidified at a temperature substantially the same as its melting point.The specific (floating) position of the nipple in the electrode sectionsocket, previously provided by the centering jig, was maintained by thesolidification of the pitch which also tightly fixed the nipple in theelectrode section socket. The pre-assembly was thus in the desiredcondition for subsequent employment in an electrode joint by couplingthe pre-assembly to a second electrode section.

An obvious danger of shipping an electrode-nipple pre-assembly is thepossibility of damage while in transit. This can be overcome in thepresent invention by protecting the entire exposed machined threadedportion and end or face of the nipple (and typically also, the electrodesection face as well) with asuitable covering, such as moldedpolyurethane foamed resin. The opposite socketed end of the electrodesection of the pre-assembly, which is internally threaded may also betypically covered, such as with a standard type end protector, viz.cardboard taped to the face. These coverings are, of course, removedbefore the pre-assembly is added to the other electrode section of thejoint. I

The pre-assembly is coupled to a second electrode section as illustratedschematically in FIG. 4. This is accomplished by threading theprojecting end of the nipple into the socket of the second electrodesection until the end faces. of the two sections joined by the nippleare in planar contact. It will be noted that in the illustratedcondition the joint has just been made and the pre-assembly of theelectrode section 2 and nipple 1 are at the top of the joint and thesecond electrode second 20 to which the pre-assembly is joined is at thebottom of the joint. This relative position of the electrode sections isessential to the success of the joints made according to the presentinvention. The second electrode section to which the pre-assembly isconnected is the upper electrode in the column of electrodes foranelectric arc furnace prior to this threading step, after which, ofcourse, the electrode section of the pre-assembly becomes the upperelectrode in the column. The making of the joint and the relativepositions of the electrode sections applies both to on furnace and offfurnace assembling techniques. The material in clearance space and hole8 in this FIG. 4 is still in its solidified condition and has not yetmelted.

When the thus assembled joint is then heated up, as it is when it isused in an electrode column of a steel furnace, the joint first reachesa temperature which is sufficiently high so as to melt the pitch andthus cause a downward flowing of a portion thereof from clearance space5 through hole 8 toward a corresponding clearance space 5a between theother end of the nipple l and the bottom of the socket in electrodesection 20. (In the embodiment of FIG. 30 the pitch would still flowtoward the lower clearance space, even though the exit end of the holeterminates at the surface threads of the nipple rather than at the otherend face of the nipple). When the pitch thus melts in this embodimentmost of it flows into clearance space 5a but some of it also stays inclearance space 5, particularly at the peripheral portions thereof. Whenthe joint is then further heated the pitch in both clearance spacesbecomes solid and carbonized, thereby locking the nipple in each of thesockets of the joined electrode sections.

There are several materials which may be used in the present inventionto fill the space 5 between the base of the nipple and the base of theelectrode section socket in order to float the nipple in the socket ofthe elecand in order to be functionable later in the locking sections tothe nipple when the pre-assembly is incorporated in an electrode jointand the joint is heated in operation. Pitches and tars are particularlysuitable.

In any case the material to be used must be one which is a solid atambient temperatures (and preferably also up to a temperature of atleast about 50C), must be one which will readily melt or flow as anon-gaseous fluid when heated (preferably at relatively low temperaturessuch as between about C and about C), (so that it can be readilyutilized in preparing the preassembly and also later in preparing theelectrode joint), must be one which will resolidify when cooled toambient temperatures (and preferably by the time it reaches atemperature of about 80C, must be one which is carbonizable (i.e. onethat leaves a substantial amount of carbon residue upon heating so thatit can perform its locking function in the preparation of the electrodejoint when the joint is heated to a temperature hot enough to re-meltthe material and then to carbonize it), and must be one which does notundergo significant expansion, such as of a foaming" type, when changingfrom the liquid to the solid state (so that its volume does not changesubstantially in going back from the solid to the liquid state when theelectrode joint is heated in operation).

The preferred materials contain substantial amounts of pitch, such asall pitch, or pitch-carbon flour combinations, or pitch-mixed with minoramounts of carbon aggregate and plasticizer, for example, a mixturecomprised of at least about 50 parts pitch and up to about 50 partscarbon aggregate, preferably flour", the term flour" typicallydesignating a material having a particle sizing such that all of itwould pass through a 20 mesh Tyler screen, a maximum of I percent wouldbe retained on a 35 mesh screen, and 50 to 55 percent of it would passthrough a 200 mesh screen. The pitch may be either coal tar pitch orpetroleum pitch. Carbon aggegate" is intended to include such materialsas finely ground graphite particles (preferred) finely ground calcinedor raw petroleum coke particles, finely ground coal particles andmixtures, the carbon aggregate preferably also all being 10 Tyler mesh.

The material may also include a minor percentage of plasticizer, such asup to about 5 percent by weight of the carbonizable material or pitch,in order to produce a less brittle pre-assembly. Typical materials thatmight be used as plasticizers or plasticizing agents include stearicacid, kerosene, tars and pitches of lower melting point, etc.

When an electrode section-nipple pre-assembly as described herein isadded to a second electrode section of an electric arc furnace column ortrain, the, nipple in the resulting three-membered joint (viz. twoelectrode sections with the nipple half-threaded into each) will be solocated that there will be a substantially even distribution ofclearance between the idle flanks of the threads of both halves of thenipple'in the electrode section sockets of the final joint assembly,rather than the common and objectionable condition typically encounteredinthe prior art of no clearance at the idle flank of the threads of thenipple-half assembled first and maximum clearance at the idle flank ofthe threads of the second nipple-half assembled. Consequently, there isa reduction in the terminal stresses between the nipple and theelectrode sections into which it is threaded with the result that thereis a reduction in the degree of splitting and breakage of the joint infurnace operation.

The net efiect, therefore, of centering or balancing the nipple in thejoint, is that there are fewer mechanical breakdowns or failures in theoperation of the furnace. There are also other advantages inherent inmaking the nipple-electrode section pro-assemblies and joints inaccordance with the present invention. For example, the incidence ofthread stripping from the sockets of the threaded electrode sections isvirtually precluded because of the more uniform thread loading attendingthe centering of the nipple. Also, the same material that is used in thepreparation of the pre-assembly acts to lock the joint in a tightposition upon its use in the furnace thus further acting to preventunwinding of the electrode joint and thus carrying out two distinctfunctions which in prior art practices were only capable -of beingperformed by two separate and distinct solutions for the two problemsof: (a) nipple balancing; and (b) nipple fixing in the sockets of theelectrode sections.

As has been indicated in connection with FIG. 3d, the possible use ofone or more holes in the nipple, in addition to the lengthwise holeillustrated in the drawings, is also within the scope of the invention.Such hole or holes may, for example, be within the nipple in one or bothends thereof and connect at an angle or intersect the hole which extendslengthwise in the nipple; or such hole or holes may take the form of aslot or slots at the surface of the nipple and extend in the lengthwisedirection of the nipple from point(s) short of the major diameter andextending to one end of the nipple so as to connect with or communicatewith the clearance space between the base of the nipple and the bottomof the electrode section socket. Such additional hole or holes orslot(s) may sometimes be desirably resorted to in order to increase thestrength of the connection between the nipple and the electrodesection(s) to which it is joined, particularly in cases where therequirement to disengage the nipple from either or both of the electrodesections to which it has been joined is not likely to occur.

An additional advantage of the present invention is that if for anyreason it is desired to unthread one of the electrode sections from thenipple (after carbonization) this may readily or controllably beaccomplished with certain of the embodiments by using untorquingpressures of the same order or at levels slightly higher than the jointassembly torque level. This is not possible with many joints of thepriorart without causing mechanical damage or destruction of one or moreof the joined members.

1. In the process of assembling an electrode joint comprising twoelectrode sections containing internally threaded sockets which extendinwardly from end faces of said sections and a correspondingly threadednipple connecting said sections by, being threaded into said sockets,the steps comprising:

a. Providing a hole starting at a point in an end face of one-half ofthe nipple and terminating at a point in the surface of the other halfof the nipple;

. pre-positioning the nipple in the socket of one of the electrodesections by threading an end thereof possessing a hole in its end faceinto the internally threaded socket so as to provide a space between thebase of the nipple and the bottom of the electrode section socket and aclearance between the non-load bearing flanks of the threads of saidthreaded nipple and the opposing faces of the threads of the electrodesocket, said non-load bearing flanks of the threads being those nearerto the ends than to the geometric center of the nipple, the other end ofsaid threaded nipple projecting outwardly from said socket;

. introducing a hot, non-gaseous fluid, carbonizable material throughthe exposed end of the hole in the projecting end of the nipple insufficient quantity so that immediately upon introduction it at leastsubstantially fills the space between the base of the nipple and thebottom of the socket of the electrode section without undergoing anysubsequent expansion;

d. permitting said hot fluid material to become substantially solid bycooling it to ambient temperature, thereby fixing the nipple in theelectrode section to provide an electrode section-nipple pre-assemblyand thereby also maintaining the pre-positioning and thread clearance of(b) and providing room for thermal expansion of the threads of theconnection;

. threading the projecting end of the nipple into the socket of thesecond electrode section until the end faces of the two sections joinedby the nipple are in planar contact, said second electrode section beingthe upper electrode in the column of electrodes for anelectric arcfurnace priorto this threading step; and

f. heating the electrode joint so that a portion of the substantiallysolid carbonizable material first becomes fluid and flows downwardlyfrom the 1 space wherein it had been introduced and solidified, throughthe hole in the nipple toward the space between the opposite end of thenipple and the bottom of the socket of the second electrode section,after which the carbonizable material becomes solid and carbonized,thereby locking the nipple in-each of the sockets of the joinedelectrode sections.

2. A process according to claim 1 wherein the hole extendslengthwise-from one end face of the nipple to the other end face.

3. A process according to claim 1 wherein the hot, fluid, carbonizablematerial includes a substantial amount of pitch.

4. A process according to claim 3 wherein the hot, fluid, carbonizablematerial consists of pitch mixed with minor amounts of plasticizer andcarbon aggregate.

5. A process according to claim 1 wherein the amount of hot, fluid,carbonizable material employed and introduced through the exposed end ofthe hole of the nipple in step c is sufiicient, before cooling, tosubstantially fill the hole in the nipple as well as the space 8. Aprocess of assembling an electrode joint according to the process ofclaim 3 wherein after step d the projecting threaded portion and theface of the nipple on one end of the pre-assembly are protected with acovering before the pre-assembly is shipped to its place of use andwherein the covering is removed before the pre-assembly is added to theother electrode section of the joint by the carrying out of steps e andfof claim 1.

2. A process according to claim 1 wherein the hole extends lengthwisefrom one end face of the nipple to the other end face.
 3. A processaccording to claim 1 wherein the hot, fluid, carbonizable materialincludes a substantial amount of pitch.
 4. A process according to claim3 wherein the hot, fluid, carbonizable material consists of pitch mixedwith minor amounts of plasticizer and carbon aggregate.
 5. A processaccording to claim 1 wherein the amount of hot, fluid, carbonizablematerial employed and introduced through the exposed end of the hole ofthe nipple in step c is sufficient, before cooling, to substantiallyfill the hole in the nipple as well as the space between the base of thenipple and the bottom of the socket of the electrode section.
 6. Aprocess accordinG to claim 3 wherein in step b the nipple ishand-tightened as far as it will go into the electrode socket and isthen back off a slight amount in the procedure of providing the threadclearance of said step.
 7. A process according to claim 3 wherein acentering jig is employed to assist in providing the prepositioning ofthe nipple and the thread clearance of step b.
 8. A process ofassembling an electrode joint according to the process of claim 3wherein after step d the projecting threaded portion and the face of thenipple on one end of the pre-assembly are protected with a coveringbefore the pre-assembly is shipped to its place of use and wherein thecovering is removed before the pre-assembly is added to the otherelectrode section of the joint by the carrying out of steps e and f ofclaim 1.